1. Field of the Invention
The present invention relates to a device for tensioning flexible elements wound onto pulleys, such as, for example, belts, cables, drive chains or also flexible elements having the function of tools, such as diamond-coated wires used in the stone-processing sector in machines for cutting marble, granite or other stone materials.
Although the present invention may find an application in numerous sectors of the art, below for the sake of simplicity of the description, specific reference will be made to the sector of machines for cutting stone materials, as mentioned above.
2. Description of the Prior Art
In this sector, for many years machines which use a diamond-coated wire have been known, said wire being mounted endlessly on two pulleys (i.e. a driving pulley and a driven pulley, called "flywheels") and, moving at high speed, being used to cut blocks or slabs of marble or granite.
The problems of tensioning the diamond-coated wire are solved, in these machines, usually by displacing the flywheel-carrying shaft (i.e. the driven shaft) with the aid of suitable moving means which are mainly hydraulic. Smaller tensioning flywheels may also be provided.
In recent years machines for producing slabs have been provided, said machines using several diamond-coated wires which are mounted on flywheels with multiple races or using a single wire which is made to pass over a multiplicity of flywheels so as to create a situation where there is a multiplicity of parallel cutting planes. Again in recent years, machines for producing slabs have been developed, said machines using a multiplicity of single diamond-coated wires which are wound endlessly onto a corresponding multiplicity of pairs of flywheels, where the adjacent flywheels are arranged very close to one another.
The problems of tensioning the diamond-coated wire in these types of machines at present have been only partially overcome or have not been overcome at all. In the case of flywheels with multiple races, tensioning is performed in a manner similar to that used in traditional single-wire machines as mentioned above. In the case of machines using multiple flywheels, the tensioning system of the known type envisages that all the driven flywheels on which the wire is partially wound are tensioned simultaneously.
This type of tensioning performed in an identical manner and simultaneously on all the flywheels may give rise to problems, some of which are serious. In particular in the following cases:
if the diameters of the flywheels are even only slightly different from those of the similar adjacent flywheels. In fact, in this case, there would be undesirable wear of the wire or deformation thereof, due to friction; PA1 if the length of the wires differs, even only slightly, from wire to wire; PA1 if the tensioning displacement of the group of flywheels is not perfectly parallel to itself; PA1 if the flywheel-carrying shaft has a camber, even of a small degree, due to the weight of the flywheels themselves, and to the load applied.
Taking into account these drawbacks, the technical problem to be solved is that of being able to perform individual and separate tensioning for each flywheel and moreover with extremely small dimensions (so that the flywheels may be arranged next to one another at a distance as required--this being the factor which determines the thickness of the slabs cut by the wire).